534 lines
19 KiB
C
534 lines
19 KiB
C
/***
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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***/
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#include <errno.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mount.h>
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#include <sys/stat.h>
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#include <sys/statvfs.h>
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#include <unistd.h>
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#include "alloc-util.h"
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#include "escape.h"
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#include "fd-util.h"
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#include "fileio.h"
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#include "hashmap.h"
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#include "mount-util.h"
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#include "parse-util.h"
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#include "path-util.h"
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#include "set.h"
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#include "stdio-util.h"
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#include "string-util.h"
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static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *mnt_id) {
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char path[strlen("/proc/self/fdinfo/") + DECIMAL_STR_MAX(int)];
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_cleanup_free_ char *fdinfo = NULL;
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_cleanup_close_ int subfd = -1;
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char *p;
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int r;
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if ((flags & AT_EMPTY_PATH) && isempty(filename))
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xsprintf(path, "/proc/self/fdinfo/%i", fd);
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else {
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subfd = openat(fd, filename, O_CLOEXEC|O_PATH);
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if (subfd < 0)
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return -errno;
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xsprintf(path, "/proc/self/fdinfo/%i", subfd);
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}
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r = read_full_file(path, &fdinfo, NULL);
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if (r == -ENOENT) /* The fdinfo directory is a relatively new addition */
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return -EOPNOTSUPP;
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if (r < 0)
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return -errno;
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p = startswith(fdinfo, "mnt_id:");
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if (!p) {
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p = strstr(fdinfo, "\nmnt_id:");
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if (!p) /* The mnt_id field is a relatively new addition */
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return -EOPNOTSUPP;
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p += 8;
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}
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p += strspn(p, WHITESPACE);
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p[strcspn(p, WHITESPACE)] = 0;
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return safe_atoi(p, mnt_id);
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}
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int fd_is_mount_point(int fd, const char *filename, int flags) {
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union file_handle_union h = FILE_HANDLE_INIT, h_parent = FILE_HANDLE_INIT;
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int mount_id = -1, mount_id_parent = -1;
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bool nosupp = false, check_st_dev = true;
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struct stat a, b;
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int r;
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assert(fd >= 0);
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assert(filename);
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/* First we will try the name_to_handle_at() syscall, which
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* tells us the mount id and an opaque file "handle". It is
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* not supported everywhere though (kernel compile-time
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* option, not all file systems are hooked up). If it works
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* the mount id is usually good enough to tell us whether
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* something is a mount point.
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*
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* If that didn't work we will try to read the mount id from
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* /proc/self/fdinfo/<fd>. This is almost as good as
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* name_to_handle_at(), however, does not return the
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* opaque file handle. The opaque file handle is pretty useful
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* to detect the root directory, which we should always
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* consider a mount point. Hence we use this only as
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* fallback. Exporting the mnt_id in fdinfo is a pretty recent
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* kernel addition.
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*
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* As last fallback we do traditional fstat() based st_dev
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* comparisons. This is how things were traditionally done,
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* but unionfs breaks this since it exposes file
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* systems with a variety of st_dev reported. Also, btrfs
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* subvolumes have different st_dev, even though they aren't
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* real mounts of their own. */
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r = name_to_handle_at(fd, filename, &h.handle, &mount_id, flags);
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if (r < 0) {
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if (errno == ENOSYS)
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/* This kernel does not support name_to_handle_at()
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* fall back to simpler logic. */
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goto fallback_fdinfo;
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else if (errno == EOPNOTSUPP)
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/* This kernel or file system does not support
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* name_to_handle_at(), hence let's see if the
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* upper fs supports it (in which case it is a
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* mount point), otherwise fallback to the
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* traditional stat() logic */
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nosupp = true;
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else
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return -errno;
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}
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r = name_to_handle_at(fd, "", &h_parent.handle, &mount_id_parent, AT_EMPTY_PATH);
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if (r < 0) {
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if (errno == EOPNOTSUPP) {
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if (nosupp)
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/* Neither parent nor child do name_to_handle_at()?
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We have no choice but to fall back. */
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goto fallback_fdinfo;
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else
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/* The parent can't do name_to_handle_at() but the
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* directory we are interested in can?
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* If so, it must be a mount point. */
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return 1;
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} else
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return -errno;
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}
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/* The parent can do name_to_handle_at() but the
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* directory we are interested in can't? If so, it
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* must be a mount point. */
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if (nosupp)
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return 1;
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/* If the file handle for the directory we are
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* interested in and its parent are identical, we
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* assume this is the root directory, which is a mount
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* point. */
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if (h.handle.handle_bytes == h_parent.handle.handle_bytes &&
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h.handle.handle_type == h_parent.handle.handle_type &&
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memcmp(h.handle.f_handle, h_parent.handle.f_handle, h.handle.handle_bytes) == 0)
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return 1;
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return mount_id != mount_id_parent;
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fallback_fdinfo:
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r = fd_fdinfo_mnt_id(fd, filename, flags, &mount_id);
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if (r == -EOPNOTSUPP)
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goto fallback_fstat;
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if (r < 0)
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return r;
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r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id_parent);
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if (r < 0)
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return r;
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if (mount_id != mount_id_parent)
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return 1;
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/* Hmm, so, the mount ids are the same. This leaves one
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* special case though for the root file system. For that,
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* let's see if the parent directory has the same inode as we
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* are interested in. Hence, let's also do fstat() checks now,
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* too, but avoid the st_dev comparisons, since they aren't
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* that useful on unionfs mounts. */
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check_st_dev = false;
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fallback_fstat:
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/* yay for fstatat() taking a different set of flags than the other
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* _at() above */
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if (flags & AT_SYMLINK_FOLLOW)
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flags &= ~AT_SYMLINK_FOLLOW;
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else
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flags |= AT_SYMLINK_NOFOLLOW;
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if (fstatat(fd, filename, &a, flags) < 0)
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return -errno;
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if (fstatat(fd, "", &b, AT_EMPTY_PATH) < 0)
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return -errno;
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/* A directory with same device and inode as its parent? Must
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* be the root directory */
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if (a.st_dev == b.st_dev &&
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a.st_ino == b.st_ino)
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return 1;
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return check_st_dev && (a.st_dev != b.st_dev);
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}
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/* flags can be AT_SYMLINK_FOLLOW or 0 */
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int path_is_mount_point(const char *t, int flags) {
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_cleanup_close_ int fd = -1;
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_cleanup_free_ char *canonical = NULL, *parent = NULL;
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assert(t);
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if (path_equal(t, "/"))
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return 1;
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/* we need to resolve symlinks manually, we can't just rely on
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* fd_is_mount_point() to do that for us; if we have a structure like
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* /bin -> /usr/bin/ and /usr is a mount point, then the parent that we
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* look at needs to be /usr, not /. */
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if (flags & AT_SYMLINK_FOLLOW) {
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canonical = canonicalize_file_name(t);
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if (!canonical)
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return -errno;
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t = canonical;
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}
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parent = dirname_malloc(t);
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if (!parent)
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return -ENOMEM;
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fd = openat(AT_FDCWD, parent, O_DIRECTORY|O_CLOEXEC|O_PATH);
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if (fd < 0)
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return -errno;
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return fd_is_mount_point(fd, basename(t), flags);
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}
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int umount_recursive(const char *prefix, int flags) {
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bool again;
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int n = 0, r;
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/* Try to umount everything recursively below a
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* directory. Also, take care of stacked mounts, and keep
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* unmounting them until they are gone. */
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do {
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_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
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again = false;
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r = 0;
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proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
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if (!proc_self_mountinfo)
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return -errno;
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for (;;) {
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_cleanup_free_ char *path = NULL, *p = NULL;
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int k;
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k = fscanf(proc_self_mountinfo,
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"%*s " /* (1) mount id */
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"%*s " /* (2) parent id */
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"%*s " /* (3) major:minor */
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"%*s " /* (4) root */
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"%ms " /* (5) mount point */
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"%*s" /* (6) mount options */
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"%*[^-]" /* (7) optional fields */
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"- " /* (8) separator */
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"%*s " /* (9) file system type */
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"%*s" /* (10) mount source */
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"%*s" /* (11) mount options 2 */
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"%*[^\n]", /* some rubbish at the end */
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&path);
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if (k != 1) {
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if (k == EOF)
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break;
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continue;
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}
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r = cunescape(path, UNESCAPE_RELAX, &p);
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if (r < 0)
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return r;
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if (!path_startswith(p, prefix))
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continue;
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if (umount2(p, flags) < 0) {
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r = -errno;
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continue;
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}
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again = true;
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n++;
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break;
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}
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} while (again);
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return r ? r : n;
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}
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static int get_mount_flags(const char *path, unsigned long *flags) {
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struct statvfs buf;
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if (statvfs(path, &buf) < 0)
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return -errno;
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*flags = buf.f_flag;
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return 0;
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}
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int bind_remount_recursive(const char *prefix, bool ro) {
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_cleanup_set_free_free_ Set *done = NULL;
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_cleanup_free_ char *cleaned = NULL;
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int r;
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/* Recursively remount a directory (and all its submounts)
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* read-only or read-write. If the directory is already
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* mounted, we reuse the mount and simply mark it
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* MS_BIND|MS_RDONLY (or remove the MS_RDONLY for read-write
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* operation). If it isn't we first make it one. Afterwards we
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* apply MS_BIND|MS_RDONLY (or remove MS_RDONLY) to all
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* submounts we can access, too. When mounts are stacked on
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* the same mount point we only care for each individual
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* "top-level" mount on each point, as we cannot
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* influence/access the underlying mounts anyway. We do not
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* have any effect on future submounts that might get
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* propagated, they migt be writable. This includes future
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* submounts that have been triggered via autofs. */
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cleaned = strdup(prefix);
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if (!cleaned)
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return -ENOMEM;
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path_kill_slashes(cleaned);
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done = set_new(&string_hash_ops);
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if (!done)
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return -ENOMEM;
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for (;;) {
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_cleanup_fclose_ FILE *proc_self_mountinfo = NULL;
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_cleanup_set_free_free_ Set *todo = NULL;
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bool top_autofs = false;
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char *x;
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unsigned long orig_flags;
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todo = set_new(&string_hash_ops);
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if (!todo)
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return -ENOMEM;
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proc_self_mountinfo = fopen("/proc/self/mountinfo", "re");
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if (!proc_self_mountinfo)
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return -errno;
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for (;;) {
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_cleanup_free_ char *path = NULL, *p = NULL, *type = NULL;
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int k;
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k = fscanf(proc_self_mountinfo,
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"%*s " /* (1) mount id */
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"%*s " /* (2) parent id */
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"%*s " /* (3) major:minor */
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"%*s " /* (4) root */
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"%ms " /* (5) mount point */
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"%*s" /* (6) mount options (superblock) */
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"%*[^-]" /* (7) optional fields */
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"- " /* (8) separator */
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"%ms " /* (9) file system type */
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"%*s" /* (10) mount source */
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"%*s" /* (11) mount options (bind mount) */
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"%*[^\n]", /* some rubbish at the end */
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&path,
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&type);
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if (k != 2) {
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if (k == EOF)
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break;
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continue;
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}
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r = cunescape(path, UNESCAPE_RELAX, &p);
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if (r < 0)
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return r;
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/* Let's ignore autofs mounts. If they aren't
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* triggered yet, we want to avoid triggering
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* them, as we don't make any guarantees for
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* future submounts anyway. If they are
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* already triggered, then we will find
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* another entry for this. */
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if (streq(type, "autofs")) {
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top_autofs = top_autofs || path_equal(cleaned, p);
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continue;
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}
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if (path_startswith(p, cleaned) &&
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!set_contains(done, p)) {
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r = set_consume(todo, p);
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p = NULL;
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if (r == -EEXIST)
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continue;
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if (r < 0)
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return r;
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}
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}
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/* If we have no submounts to process anymore and if
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* the root is either already done, or an autofs, we
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* are done */
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if (set_isempty(todo) &&
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(top_autofs || set_contains(done, cleaned)))
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return 0;
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if (!set_contains(done, cleaned) &&
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!set_contains(todo, cleaned)) {
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/* The prefix directory itself is not yet a
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* mount, make it one. */
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if (mount(cleaned, cleaned, NULL, MS_BIND|MS_REC, NULL) < 0)
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return -errno;
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orig_flags = 0;
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(void) get_mount_flags(cleaned, &orig_flags);
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orig_flags &= ~MS_RDONLY;
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if (mount(NULL, prefix, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0)
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return -errno;
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x = strdup(cleaned);
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if (!x)
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return -ENOMEM;
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r = set_consume(done, x);
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if (r < 0)
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return r;
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}
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while ((x = set_steal_first(todo))) {
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r = set_consume(done, x);
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if (r == -EEXIST || r == 0)
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continue;
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if (r < 0)
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return r;
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/* Try to reuse the original flag set, but
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* don't care for errors, in case of
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* obstructed mounts */
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orig_flags = 0;
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(void) get_mount_flags(x, &orig_flags);
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orig_flags &= ~MS_RDONLY;
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if (mount(NULL, x, NULL, orig_flags|MS_BIND|MS_REMOUNT|(ro ? MS_RDONLY : 0), NULL) < 0) {
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/* Deal with mount points that are
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* obstructed by a later mount */
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if (errno != ENOENT)
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return -errno;
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}
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}
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}
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}
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int mount_move_root(const char *path) {
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assert(path);
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if (chdir(path) < 0)
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return -errno;
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if (mount(path, "/", NULL, MS_MOVE, NULL) < 0)
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return -errno;
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if (chroot(".") < 0)
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return -errno;
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if (chdir("/") < 0)
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return -errno;
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return 0;
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}
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bool fstype_is_network(const char *fstype) {
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static const char table[] =
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"afs\0"
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"cifs\0"
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"smbfs\0"
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"sshfs\0"
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"ncpfs\0"
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"ncp\0"
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"nfs\0"
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"nfs4\0"
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"gfs\0"
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"gfs2\0"
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"glusterfs\0"
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"pvfs2\0" /* OrangeFS */
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;
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const char *x;
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x = startswith(fstype, "fuse.");
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if (x)
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fstype = x;
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return nulstr_contains(table, fstype);
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}
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int repeat_unmount(const char *path, int flags) {
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bool done = false;
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assert(path);
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/* If there are multiple mounts on a mount point, this
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* removes them all */
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for (;;) {
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if (umount2(path, flags) < 0) {
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if (errno == EINVAL)
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return done;
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return -errno;
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}
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done = true;
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}
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}
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